The invention relates to an identification device in the form of a tag-like strip affixable to an article and comprising at least one inductive member formed of flat conductor strips and one capacitive member formed of superposed conductor strip portions with a dielectric interposed therebetween, said capacitive member forming with the inductive member a closed resonant circuit.
Identification devices of this type have been known, for example, from German AS 2,826,861. They essentially contain an electric parallel resonant circuit and are contemplated for generating characteristic signals permitting the identification thereof in a high frequency electromagnetic field. Such passive identification devices are used in production engineering for identifying work pieces, in analysis technology for identifying samples, as safeguarding means and as identifying sensors in product safeguarding systems, especially antitheft systems.
When such devices are required in very large numbers the manufacturing costs are of essential significance to the economical use of the system. The conventional identification devices are manufactured, for example, by etching conductor strips out of metal foils applied on both sides of a flexible, electrically non-conductive carrier sheet. The etched conductor strips form the required inductive member, while the capacitive member of the resonant circuit is formed by distributed capacities formed by opposed conductor strip portions and the interposed dielectric carrier sheet. In order to connect the conductor strips on the two sides of the carrier sheet so that together they cooperate to form an inductive member, contact through the carrier sheet is necessary. Furthermore, manufacturing methods requiring etching on both sides are very expensive and contact through the sheet requires a piece-by-piece check of each individual resonant unit.